1. Field of the Invention
This invention relates to an elastomeric device that is used in the oral cavity during orthodontic treatment. More particularly, the present invention is directed to an elastomeric orthodontic force module that is useful for moving one or more teeth to desired locations along a dental arch, or for moving one dental arch relative to the other.
2. Description of the Related Art
Orthodontia is a specialized field within the general subject area of dentistry. Orthodontic treatment involves movement of malpositioned teeth to correct locations along the dental arch. In some instances, orthodontic treatment also includes movement of one dental arch as a unit relative to the other dental arch. Orthodontic treatment can result in improved occlusion as well as a more pleasing aesthetic appearance.
One type of orthodontic treatment involves the use of a set of components that are collectively known as “braces”. In this type of treatment, small slotted devices known as brackets are secured to the patient's anterior, cuspid and bicuspid teeth. An archwire is received in the slots of the brackets and forms a track to guide movement of the teeth to desired positions.
Ends of orthodontic archwires are often received in enclosed passageways of small devices known as buccal tubes that are connected to the patient's molar teeth. The passageways of buccal tubes help prevent the ends of the archwire from contacting the patient's soft tissue in the oral cavity, which might otherwise lead to pain and injury. More importantly, buccal tubes often serve as points of connection for components that apply forces in the oral cavity, since the molar teeth associated with the buccal tubes have relatively large roots. These large roots provide relatively stable anchorage against the applied forces so that the other teeth connected to the force components are moved as a result.
A number of options are available during orthodontic treatment for applying forces to teeth in order to move the teeth to desired positions. Oftentimes, the practitioner will use the inherent resiliency of the archwire to apply a force to one or more brackets and move the associated teeth as the archwire tends to return to its normal relaxed configuration. If desired, one or more loops, bends, twists or other configurations may be formed in the archwire by the practitioner in order to help guide movement of the teeth as desired.
In some instances, orthodontic treatment may include correction of the alignment of the upper dental arch with the lower dental arch. For example, certain patients have a condition referred to as a Class II malocclusion wherein the lower dental arch is located an excessive distance in a rearward direction relative to the location of the upper dental arch when the jaws are closed. Other patients have an opposite condition referred to as a Class III malocclusion wherein the lower dental arch is located in a forward direction of its desired location relative to the position of the upper dental arch when the jaws are closed.
Orthodontic treatment of Class II and Class III malocclusions is commonly undertaken by movement of the upper dental arch as a single unit relative to movement of the lower dental arch as a single unit. To this end, forces are often applied to each dental arch as a unit by applying force to the brackets or buccal tubes, the archwires, or attachments that are connected to the brackets, buccal tubes or archwires. In this manner, a Class II or Class III malocclusion can be corrected at the same time that the archwires and brackets are used to move individual teeth along the dental arch to desired positions relative to each other.
Correction of Class II and Class III malocclusions is sometimes carried out by use of a force-applying system known as headgear. Headgear often includes strapping that extends around the rear of the patient's head. The strapping is often connected to tension springs that, in turn, are connected to the buccal tubes, the brackets, or one of the archwires. Additionally, and as an alternative for correction of Class III malocclusions, the strapping may be connected by tension springs to a chin cup that externally engages the patient's chin. In either instance, the strapping and springs serve to apply a rearwardly-directed force to the associated jaw.
However, headgear is often considered unsatisfactory because it is visibly apparent. Headgear may serve as a source of embarrassment, particularly among adolescent patients who may experience teasing from classmates. The embarrassment can be somewhat reduced if the orthodontist instructs the patient to wear the headgear only at night. Unfortunately, such practice may lengthen treatment time since the desired corrective forces are applied during only a portion of each calendar day.
Consequently, many practitioners and patients favor the use of intra-oral devices for correcting Class II and Class III malocclusions. Such devices are often located near the cuspid, bicuspid and molar teeth and away from the patient's anterior teeth. As a result, intra-oral devices for correcting Class II and Class III malocclusions are hidden in substantial part once installed and eliminate much of the patient embarrassment that is often associated with headgear.
A variety of force modules are known for treatment of Class II and Class III malocclusions. U.S. Pat. No. 6,120,289 describes a force module in the shape of a flat spring that assumes a curved orientation along its length when the patient's jaws are closed. During use, the inherent resiliency of the module tends to urge the module toward its normally straight configuration and as a result move the associated dental arches relative to each other.
Other types of force modules for correction of Class II and Class III malocclusions include telescoping assemblies that may optionally include a spring. An example of an improved telescoping force module is described in applicant's U.S. Pat. No. 5,964,588. In devices of this general type, the dental arches are moved relative to each other by the force of a coil spring or by a dead stop when the piston reaches the bottom of the cylinder, or by a combination of both.
Orthodontic force modules made of an elastomeric material have also been used in the past to treat Class II and Class III malocclusions. Elastomeric force modules are connected between the dental arches and often used in tension to pull the jaws together. The tension applied by the module tends to pull the jaws together in a direction along a reference line that extends between the points of attachment of the force module.
A variety of elastomeric orthodontic force modules are known. Examples of such force modules include bodies having the shape of a large O-ring and chain-type modules made of a number of smaller O-rings that are integrally connected together. Other types of elastomeric force modules include “dogbone-shaped” modules having a central, elongated straight section and a round eyelet section connected to each end of the straight central section.
While the elastomeric force modules described in the preceding paragraphs are generally considered satisfactory by many orthodontic practitioners, there is a continuing need in the art to improve the force modules that are currently available. For example, it would be desirable to provide an improved force module that is more resistant to fracture at a given tensile load without increasing the overall stiffness of the module. To this end, many attempts have been made to find alternative elastomeric materials that would be suitable for use in the oral cavity as force modules. To date, however, few orthodontic force modules with alternative materials are available.